Method for data exchanging data between a field device and a control device via internet

ABSTRACT

In a method for data exchange between a field device  1, 2, 3, 4  and a control device  50  via Internet  20 , modem  13, 14  and public telephone network  30 , the current IP-address of the modem  13, 14  is transmitted to the distributor-server  45  over the public telephone network. Field device queries by the control device  50  to a permanent address of the field device are forwarded via the current IP-address to the field device  1, 2, 3, 4.

The invention relates to a method for exchanging data between a fielddevice and a control device via Internet.

In process control engineering, field devices are in many cases deployedto register and influence process variables. Examples of field devicesinclude temperature measurement devices that record temperature of aprocess medium, flow-meters that record the flow of a process medium ina pipeline section, or fill level meters that determine the fill levelof a liquid or a bulk solid in a container.

In addition to merely transmitting measurements, field devices alsoallow the transmission of various kinds of information stored in thefield device, e.g. parameters (zero point, measurement range, etc.),measurement curves and diagnostic information. The parameters can beadjusted from a control device (configuring and parametering). Withevery initial installation or with a device exchange, a field devicemust be configured and parameterized.

Often, access to field devices over larger distances is desired. Onepossibility is to connect the field device and the control device, eachwith a modem, over a public communication network. The modem can also bedirectly integrated in the field device. Alternatively, the field deviceis not directly connected to the communication network, but, instead,through a gateway. The data transmission occurs e.g. over the publictelephone network (analog grid, ISDN, GSM or UMTS). With greaterdistances, this means, however, telephone costs accumulating as afunction of connection time.

An Internet connection is cheaper. With this, the modem on the fielddevice side itself dials over the public telephone network to thenearest Internet-Service Provider. Over the Internet, multiple users canalso simultaneously access the field device. The control device, whichis either connected with the Internet over a modem or else connecteddirectly with the Internet, can then access the field device data usingthe appropriate IP-address of the modem. For example the current fielddevice measurement can be queried by the control device via theHTML-page http://195.123.123.123/measurement1.html, where the IP-addressof the field device is 195.123.123.123. This only incurs telephone costsfor the connection to the nearest Internet-Service-Provider. Thedisadvantage here is that the IP-address of the modem is notpredetermined, but instead is newly assigned by theInternet-Service-Provider from its IP address pool with each dialinginstance. This means that, in order to access, the user must change theIP-Address of the field device with each dialing instance. This isundesirable from the point of view of the user.

An object of the invention is, therefore, to provide a method for dataexchange between a field device and a control device via the Internet,such that the field device always can be contacted over the samepermanent address in a way that is cost-effective and simple toimplement.

This object is achieved by a method according to claim 1 or 3.

An essential idea of the invention is that a distributor-server forwardsto the current IP-address of the field device, field device inquiriesdirected to a permanent address. In this way, a specific field device isalways contacted via the same permanent address. Since the modem is onlyoccasionally connected to the Internet-Service-Provider, the telephonecosts are relatively small.

Advantageous further developments are given in the dependent claims.

In an alternative embodiment, a periodic query of the field device isperformed by the distributor-server. The field device data areintermediately stored on the distributor-server. By way of a fielddevice query, the user can retrieve the field device information fromthe distributor-server.

With this, no delays develop because of having to assemble theconnection.

The invention will now be explained in greater detail on the basis ofthe drawings, whose figure shows multiple field devices connected with acontrol device via the Internet.

FIG. 1 shows a plurality of field devices 1,2,3,4 connected with aInternet-Service-Provider 40 a via a gateway 55 and modem 13, or a modem14, and the public telephone network.

The Internet-Service-Provider 40 a enables the connection to theInternet 20. A control device 50 is also connected to the Internet 20through an Internet-Service-Provider 40 b. The control device 50, e.g. aPC-based measurement collection system, allows communication with thecurrent Internet protocols (TCP/IP and HTTP). The control device 50 cancommunicate with the field devices 1,2,3,4 over a HTTP-Client (e.g. astandard Web browser). Gateway 55 and field device 4 are able tocommunicate with the current Internet protocols (TCP/IP, HTTP, SMTP).Field device 4 and the gateway 55 each use a web-interface with anintegrated web-server (e.g. HTTP-server). The field device 1-4 and thegateway 55 each have a permanent address over which they can becontacted.

Besides connecting the control device 50 via anInternet-Service-Provider 40 b, a direct connection with the Internet 20is also possible.

A distributor-server 45 is, on the one hand, directly connected with theInternet 20, and, additionally, connected via one or more modems (here11, 12) with the public telephone network 30.

The configuration of the distributer-server 45 will now be explained ingreater detail.

The user calls-up the page of the distributor-server 45(www.distributorserver.com) from the control device 50 using a Webbrowser. An authentication and password query is a possible securitymechanism. Using an input form, a new field device can be installed oran already-installed field device can be accessed and its configurationdata changed. The configuration data include the telecommunicationsconnect-number of the corresponding modem, the permanent address offield device, designation of an alternative access name for the fielddevice, respectively gateway, possibly with branched structure fordescribing a measurement location (access e.g. via:www.distributorserver.com/mainmeasurement.cgi?Site=TankFarm111&TankNo.14), the activating or deactivating of the periodic collectionof the field device data for mirroring the data of the field device orthe gateway in the distributor-server 45 and simulation of the devicebehavior in a query to the permanent IP-address by access to the storeddevice information, the query cycle of the device data needed for themirroring, in time units (hours, minutes) and specification of thenumber of ring procedures until the field device 4, respectively thegateway 55, dials into the Internet 20.

The distributor-server 45 does not necessarily have to be configuredover the Internet. It can also be configured directly by theadministrator of the distributor-server 45.

The method of the invention will now be explained in greater detail onthe basis of a field device query to a field device that is connecteddirectly with a modem. A query to a field device that is connectedthrough a gateway with a modem proceeds correspondingly.

A field device query to a permanent address of the field device is sentfrom the control device 50 to the distributor-server 45 via Internet.The field device query for collecting the main measurement of the fielddevice 4 can read as follows:www.distributorserver.com/mainmeasurement.cgi? PA=11074EBB76, whereinthe permanent address of the field device 4 corresponds to itsHART-address, which reads 11074EBB76.

The distributor-server 45 then dials the modem 14. This dialing occursafter the distributor-server has searched its internal database for thepermanent address 11074EBB76 and has determined the correspondingtelecommunications connection number of the modem 14. The modem 14 nextlogs-in at the Internet-Service-Provider 40 a and transfers the currentIP-address to the distributor-server 45 e.g. via the callwww.distributorserver.com/DynamicIP.cgi? PA=11074EBB76 &IP=168.33.127.11. The distributor-server 45 forwards the field devicequery to the current IP-address of the field device 4 by the callhttp://168.33.127.11/mainmeasurement.cgi? PA=11074EBB76.

The control device 50 is now directly connected with the field device 4.

In this way, the user can, in simple manner, contact the field device 4from the control device 50 and, so, query data from the field device 4,respectively transfer data to the field device 4, without knowing thecurrent IP-address of the field device 4.

In an alternative embodiment of the invention, the field device data aremirrored in the distributor-server 45. For this, the distributer-server45 dials the modem 14 on a regular schedule, following which the fielddevice dials into the Internet and reports its current IP-address to thedistributer-server 45. Then the distributor-server can access the fielddevice 4 over the Internet and intermediately store the currentinformation of the field device 4.

In this embodiment, the user likewise only dials the permanent addressof the field device 4 and can then retrieve the information of the fielddevice 4 stored in the distributor-server 45. In this way, there are nodelays caused by having to assemble the telephone connection.

Since the user needs the information only at certain times, it makessense that the query to the distributer-server 45 can be configured bythe user him-, her- or itself.

1-3. (canceled)
 4. A method for data exchange between a field device,which is connected with the Internet over a modem and the publictelephone network, and a control device, which is likewise connectedwith the Internet, comprising the steps of: a) Sending a field devicequery, directed to a permanent address of the field device, from thecontrol device to a distributor-server via the Internet; b) dialing themodem from the distributor-server; c) log-in of the modem at anInternet-Service-Provider and transmission of the current IP-address ofthe field device to the distributor-server; and d) forwarding the fielddevice query to the current IP-address of the field device.
 5. Themethod as claimed in claim 4, wherein: a plurality of field devices areconnected over a gateway with the modem.
 6. The method for data exchangebetween a field device, which is connected over a modem and the publictelephone network with the Internet, and a control device, which islikewise connected with the Internet, comprising the steps of: a)periodic collecting of the field device information of the field deviceby the distributor-server; b) intermediately storing the field deviceinformation in the distributor-server; and c) transmitting the fielddevice information in the case of a field device query to the permanentaddress of the field device by the control device.